Chapter 1 Homeostasis Recall the concept and components of homeostatic systems, describing how cells, tissues, organs and organ systems maintain important

Chapter 1Homeostasis

• Recall the concept and components of homeostatic systems, describing how cells, tissues, organs and organ systems maintain important physiological set points. This will be measured by quiz and exam scores.

Outline

• Physiology• Levels of organization• Basic Cell function• Tissues• Body systems• Homeostasis

Physiology• Study of body functions

• Two processes explain body functions– Teleological

• Explanations are in terms of meeting a bodily need

– Mechanistic• Explanations are in terms of cause and effect

sequences– Body is viewed as a machine

Physiology is the study of body functions

•Physiologists explain body function in terms of cause-and-effect sequences

Two approaches are used to explain events that occur in the body: – The purpose of a body process – The underlying mechanism

•Anatomy is the study of structure

•Physiology and anatomy are interrelated because functions depend on structure

Structure-Function relationships of the body Examples:•Heart receiving and pumping blood•Teeth tearing and grinding food

Levels of Organization-Cells

Basic Cell Functions• Obtain nutrients and oxygen from surrounding environment• Perform chemical reactions that provide energy for the cell• Eliminate carbon dioxide and other wastes to surrounding

environment• Synthesize needed cellular components• Control exchange of materials between cell and its

surrounding environment• Sensing and responding to changes in surrounding

environment• Reproduction

– Exception• Nerve cells and muscle cells lose their ability to

reproduce during their early development

Why Study Cells?

• Stem Cell Research (pg 10)

• 5 minutes

Tissues• Groups of cells with similar structure and

specialized function

• Four primary types of tissues– Muscle tissue

– Nervous tissue

– Epithelial tissue

– Connective tissue

Tissues• Muscle tissue

– Specialized for contracting and generating force

– Three types of muscle tissue• Skeletal muscle

– Moves the skeleton

• Cardiac muscle– Pumps blood out of the heart

• Smooth muscle– Encloses and controls movement of contents through hollow

tubes and organs

• Connective tissue– Cells dispersed in a matrix

– Connects, supports, anchors tissue

Tissues• Nervous tissue

– Consists of cells specialized for initiating and transmitting electrical impulses

– Found in brain, spinal cord, and nerves

• Epithelial tissue– Consists of cells specialized for exchanging

materials between the cell and its environment

– Organized into two general types of structures• Epithelial sheets

• Secretory glands

Fig. 1-4a, p. 7

Sweat gland duct in the skin. LM X5.

Credit: © Carolina Biological/Visuals Unlimited 318237

Simple Squamous Epithelium. LM X75.

Credit: © Carolina Biological/Visuals Unlimited

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Microscopic technique series - Cheek cells. Phase view. LM X75.

Credit: © David Phillips/Visuals Unlimited 308777

Stratified squamous epithelium from mouth mucosa. H&E stain. LM X100.

Credit: © G.W. Willis, MD/Visuals Unlimited

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Human pseudostratified columnar epithelium lining the bronchus of the lung. H&E stain. X180.


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Areolar (loose) connective tissue. LM X60.


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Hyaline cartilage. X64.

Credit: © Dr. Fred Hossler/Visuals Unlimited

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Collagen or dense connective tissue. X155.

Credit: © Dr. David Phillips/Visuals Unlimited

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Reticular fibers, silver preparation. X100.

Credit: © Dr. Richard Kessel/Visuals Unlimited

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Human unilocular (white) fat and adipose (adult fat). H&E stain. LM X100.


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Bone section showing osteocytes in lacunae arranged in concentric circles surrounding Haversian canals. LM X75.


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Organs• Consist of two or more types of primary

tissues that function together to perform a particular function or functions

• Example– Stomach

• Inside of stomach lined with epithelial tissue

• Wall of stomach contains smooth muscle

• Nervous tissue in stomach controls muscle contraction and gland secretion

• Connective tissue binds all the above tissues together

Levels of Organization-Organs

• Organs are combinations of two or more types of tissues that function together

An example is the stomach: – Lined with epithelial tissue

– Wall contains smooth muscle and nervous tissues

– Connective tissue binds various tissues together

Body Systems• Groups of organs that perform related

functions and interact to accomplish a common activity essential to survival of the whole body

• Do not act in isolation from one another

• Human body has 11 systems

Body Systems

• Circulatory System• Digestive System• Respiratory System• Urinary System• Skeletal System• Muscular System

• Integumentary System

• Immune System• Nervous System• Endocrine System• Reproductive System

Information from the external environment relayed through thenervous system

O2

CO2

Urine containingwastes and excess water and electrolytes

Nutrients, water,electrolytes

Feces containingundigested foodresidue

Sperm leave maleSperm enter female

EXTERNALENVIRONMENT

BODY SYSTEMS

RESPIRATORY SYSTEM

NERVOUS SYSTEM

URINARY SYSTEM

DIGESTIVE SYSTEM

REPRODUCTIVE SYSTEM

Exchanges with all other systems

CIRCULATORY SYSTEM

Exchanges with all other systems

MUSCULAR AND SKELETAL

SYSTEM

IMMUNE SYSTEM

INTEGUMENTARY SYSTEM

ENDOCRINE SYSTEM

Body systemsmaintainhomeostasis

Keeps internalfluids in

Keeps foreignmaterials out

HOMEOSTASIS

Homeostasisessential forcell survival

CELLS

Cells makeup bodysystem

Enables thebody to interactwith the externalenvironment

Protects againstforeign invaders

Regulate

What contribution does each system make to whole body homeostasis?

Homeostasis vs. Allostasis

• Homeostasis– ideal set point through local regulatory mechanism

• Claude Bernard 1865 and Walter Cannon 1926

– ex. Kidneys figure this out and decrease fluid output

• Allostasis:– The brain coordinating body-wide changes often including

changes in behavior.

– “remaining stable by being variable” – Sterling and Eyer 1988.

Sterling, P.; Eyer, J. (1988). "Allostasis: A new paradigm to explain arousal pathology". In Fisher, S.; Reason, J. T. Handbook of life stress, cognition, and health. Chicester, NY: Wiley.

Concept of Homeostasis

• Homeostasis defined as maintenance of a relatively stable internal environment

– Does not mean that composition, temperature, and other characteristics are absolutely unchanging

• Homeostasis is essential for the survival of each cell

• Each cell helps maintain the internal

• environment shared by all cells

• Factors maintained homeostatically:– concentration of nutrients

– concentration of O2 and CO2

– concentration of waste products

– pH

– concentrations of water, salt, and other electrolytes

– volume and pressure

– temperature

Fluid Compartments

• The fluid inside the cell is intracellular fluid (ICF)

• The fluid outside the cells is extracellular fluid (ECF)– ECF is the body’s internal

environment

• Consists of the plasma and interstitial fluid Most body cells are not in direct contact with the external environment

• Cell survival depends on maintaining a relatively stable internal fluid environment

Homeostatic Control Systems

• In order to maintain homeostasis, control system must be able to– Detect deviations from normal in the internal

environment that need to be held within narrow limits

– Integrate this information with other relevant information

– Make appropriate adjustments in order to restore factor to its desired value


• Control systems are grouped into two classes– Intrinsic controls

• Local controls that are inherent in an organ

– Extrinsic controls• Regulatory mechanisms initiated outside an organ

• Accomplished by nervous and endocrine systems


• Feedforward – Term used for responses made in anticipation of

a change

• Feedback – Refers to responses made after change has been

detected

– Types of feedback systems• Negative

• Positive


• Negative feedback system– Primary type of homeostatic control

– Opposes initial change

– Components• Sensor

– Monitors magnitude of a controlled variable

• Control center– Compares sensor’s input with a set point

• Effector – Makes a response to produce a desired effect


• Positive feedback system– Amplifies an initial change– Do not occur as often as negative feedback system– Example

• Uterine contractions become increasingly stronger until the birth of the baby

• Pathophysiology refers to abnormal functioning of the body

associated with diseaseWhen a homeostatic disruption becomes so severe

that it is no longer compatible with survival, death results

Documents

Chapter 1 Homeostasis Recall the concept and components of homeostatic systems, describing how cells, tissues, organs and organ systems maintain important